1. Field of the Invention
The present invention generally relates to footwear, and more particularly to methods for constructing an article of footwear and products manufactured according to such methods.
2. Background Art
Typically, a shoe, such as an athletic shoe, includes an upper and a sole. The upper is that part of the shoe which covers and protects the heel, instep, toe and side portions of the foot. The upper is secured to the wearer's foot by a closure system which typically includes a lacing means, buckles, or hook and loop-type fasteners, such as VELCRO fasteners. The closure system of the upper is conventionally positioned above the instep portion of the foot to allow easy donning and doffing of the shoe. The sole of an athletic shoe typically includes an insole, a midsole, and an outsole.
The insole (or insole board) typically lies under a removable sockliner. The insole is the foundation of the shoe to which the upper is lasted and the sole attached.
The midsole lies between the insole and the outsole. The primary function of the midsole is to provide cushioning to the wearer's foot, specifically in the heel and forefoot regions. The midsole may be formed in one or more pieces and is the portion of the shoe that provides most of the cushioning upon impact. A mechanism for stabilizing the heel of the foot may also be incorporated into the midsole. While recent years have brought many variations to midsole design, the principal materials used to supply cushioning include polyurethane (PU) and ethylvinyl acetate (EVA) foams.
The outsole is that part of the shoe which comes into direct contact with the ground and is the ground engaging portion of the shoe. As such, the outsole is typically made of an abrasive resistant material such as rubber. Because it is critical that the outsole exhibit certain wear resistant characteristics, there are a finite number of materials from which to make an outsole.
Conventionally, a midsole and an outsole are molded as separate components and then are glued and pressed together to form the sole of a shoe. The upper and the sole are then glued and pressed to the lasted upper to complete the shoe.
Each time the shoe of a runner contacts the ground, considerable force is transmitted through the shoe to the runner's foot. This force tends to push the foot forward in the shoe, causing discomfort. In addition, lateral forces cause relative lateral movement between the foot and the shoe. These lateral forces not only produce fatigue in the runner's foot, but also tend to stretch and wear the shoe, particularly in the metatarsal region. Also, the lateral forces can offset the upper part of the shoe from the sole such that the runner's foot is not properly aligned over the sole.
It is desired, therefore, to provide an athletic shoe with lateral and medial reinforcements which provide additional support on the sides of the foot and which, at the same time, have long life and do not restrict or cause discomfort to the wearer during vigorous and prolonged use.